ABSTRACT
A mid-infrared two-line thermometry based on H2O absorption was developed for in situ and sensitive temperature measurements of laminar flames. The H2O absorption lines in v3 fundamental band were systematically investigated and a new promising line pair (4029.52 cm–1 and 4030.73 cm–1) was selected to achieve strong absorption line-strength and high-temperature sensitivity over the temperature range of 1000–3000 K. This line pair was readily assessed by a single current scan of a distributed feedback laser near 2.5 μm. The scanned-wavelength laser absorption strategy was adopted for temperature measurements for both laminar sooting and non-sooting flames. This optical sensor was applied in measuring various flame conditions including CH4/air and C2H4/air premixed flames (Ф = 0.8–1.2), C2H4/air sooting flames (Ф = 1.78–2.38), and partially premixed flames. Our measurements were in good agreement with thermocouple measurements for all the flame conditions. In addition, numerical simulations using the detailed chemical kinetic mechanisms (CH4 flame: GRI 3.0, C2H4 flame: USC 2.0) were conducted to validate the experimental results.
Acknowledgment
The authors gratefully acknowledge the National Supercomputing Center (Shenzhen) for providing CHEMKIN-Pro (15131) software and computational facilities.
Funding
This research is supported by the National Natural Science Foundation of China (NSFC; 11502222) and Research Grants Council of the Hong Kong Special Administrative Region, China (CUHK14234116).